Wide angle d&#39;arsonval movement having core mounting means interfitted with the core ring



y 0, 1968 E. BAJARS 3,395,349

WIDE ANGLE D'ARSONVAL MOVEMENT HAVING CORE MOUNTING MEANS INTERFITTED WITH THE CORE RING Filed Feb. 10, 1964 2 Sheets-Sheet 1 CORE RING SUPPORTS FIG] FIG. IA

3 Eric Bcy'cms IN VENTOR.

July 30, 1968 E. BAJARS 3,395,349

WIDE ANGLE D'ARSONVAL MOVEMENT MEANS HAVING CORE MOUNTING INTERFITTED WITH THE CORE R Filed Feb. 10, 1964 Sheets-Sheet 2 I N VENTOR.

Eric Bcy'ars United States Patent 3,395,349 WIDE ANGLE DARSONVAL MOVEMENT HAVING CORE MOUNTING MEANS INTERFITTED WITH THE CORE RING Eric Bajars, Elmhurst, Ill., assignor to American Gage & Machine Company, Chicago, Ill., a corporation of Illinois Filed Feb. 10, 1964, Ser. No. 343,618 3 Claims. (Cl. 324-450) ABSTRACT OF THE DISCLOSURE A DArsonval type meter movement including a pair of annular permanent magnets and an annular core ring interposed between the permanent magnets. A coil is associated with the core ring, and the magnets and ring are spaced whereby free movement of the coil around the ring is possible. A mounting means is provided for supporting the core ring. The mounting means includes lateral recesses which permit interfitting relationship with a relatively narrow opening extending across the cross section of the core ring. The mounting means also includes enlarged ends received in separations defined by the permanent magnets. A cylindrical element is located in surrounding relationship with respect to the core ring, and the permanent magnets are supported at their edges by this cylindrical element. Face plates are provided on the opposite sides of each of the permanent magnets to provide magnetic circuits for influencing the movement of the coil.

This invention relates to DArsonval meter movements, and particularly to an improved moving-coil instrument wherein the design permits a large deflection angle, as

great as 270 to 300.

DArsonval movements of the so-called wide-angle type have been previously known in the art, but they have in general been characterized by awkward mechanical structure, large size, and low sensitivity as compared with narrow-angle movements of comparable electrical characteristics. Moreover, previously known wide-angle move- Inents have generally been difficult to shield effectively against external magnetic fields.

The primary object of the present invention is to provide a wide-angle DArsonval movement characterized by high sensitivity, compact and simple external geometry, effective self shielding, and striking ease of assembly.

Another object and advantage of the present invention is that it provides a wide-angle DArsonval movement that is equally well adaptable to either the jeweledwpivot or taut-band types of coil suspension. Another object of the invention is to provide a wide-angle DArsonval movement so designed that short magnets may be used and a short, self-enclosed magnetic circuit provided. A still further object of the invention is to provide a wide-angle movement design wherein the magnetization of the magnets may be easily and simply accomplished.

Still another object of the present invention is to provide a DArsonval movement assembly in which all the components of the magnetic circuit save the magnets themselves can be fashioned from soft iron or similar magnetically permeable material, the assembly requiring no nonmagnetic parts and supports.

Another object of the invention is to provide a movement assembly of the described characteristics that is characterized also by high output torque, this desirable feature being achieved by a design in which the useful air gap encloses three of the four sides of the moving coil.

Other objects and advantages of the invention will be apparent from the following detailed description of an illustrative embodiment thereof.

Such an illustrative embodiment of the invention is illustrated in the appended drawing. FIG. 1 is a view in axial section of a meter movement made according to the invention. FIG. 1A depicts an exploded showing of the various components in perspective. FIG. 2 is a fragmentary sectional view of the FIG. 1 instrument, in perspective, designed to bring out the structural inter-relation of the various parts. FIG. 3 is a semi-diagrammatic fragmentary sectional view of the FIG. 1 instrument, provided with arrows to indicate clearly the path of the flux in the magnetic circuit.

As may be seen especially well from FIGS. 1 and 1A a distinctive feature of my meter-movement assembly is the use of essentially annular magnets and associated parts, assembled coaxially to provide a self-contained, mechanically rugged sandwich. I prefer to use two magnets, generally ring-shaped but preferably relieved in a limited arcuate section to facilitate magnetic connection of the respective poles to the air-gap defining elements of the magnetic circuit. Two such magnets are respectively designated 11 and 12 in the drawing. As indicated in FIG. 3, the magnets are magnetized axially and are disposed in the assembly with like-polarity surfaces facing one another. (As shown in FIG. 3, the south poles of magnets 11 and 12 are disposed in facing relationship; it will of course be understood that the indicated polarities may be reversed if desired.)

The particular material selected for the magnets is a matter of designers choice; I have found [magnets of the so-called Alnico type to be highly satisfactory.

The facing surfaces of magnets 11 and 12 are butted against the top and bottom, respectively, of an inner assembly comprising a soft iron ring 13 and a pair of face plates 14 and 15, also fashioned of soft iron. Ring 13, as may be seen from FIGS. 1 and 1A comprises a complete ring and is internally recessed at both its upper and lower edges to provide annular seats for the face plates 14 and 15. Plates 14 and 15, as shown in both FIGS. 1A and 2, have a relieved sector generally conforming to the corresponding relieved sectors of the magnets 11 and 12.

Above and below the magnets 11 and 12 are a pair of outer face plates made of soft iron, the top plate being designated 16 and the bottom plate 17.

Sandwiched between the top and bottom plates 16 and. 17 I provide a pair of core ring supports 18 and 19, made of soft iron and dimensioned to fit snugly between the plates 16 and 17 within the sectors defined by the relieved zones of magnets 11 and 12 and plates 14 and 15. These core ring supports are provided with lateral recesses shaped to receive and hold securely an inner core ring 21, made of soft iron, ring-shaped, and relieved only in a narrow zone proportioned whereby the opposed ends of the ring defining this opening are fit snugly within the lateral recesses of the supports 18 and 19. The combination of the ring 13, magnets 11 and -12, and plates 16 and 17 pro- Vides an exterior cylindrical configuration for the unit.

Threaded over the core ring 21 is a rectangular DArsonval moving coil 22, so dimensioned as to clear both the ring 21 and the magnetic members 13, 14 and 15. (Skilled readers will recognize that the annular space between the core ring 21 and the magnetic members 13, 14 and 15 defines a magnetized air gap within which the coil 22, may, when suitably suspended, rotate freely through a large angle, which may approximate 300.)

In the embodiment herein disclosed, I have shown the coil 22 mounted for rotation by means of a conventional pivot support, comprising a spindle 23 and jeweled bearings 24, the bearings 24 being mounted in suitable apertures provided therefor at the top and bottom face plates 16 and 17. As is customary, a counterweight 25 is carried by spindle 23 to balance the mass of coil 22. In addition, the spindle 23 will normally carry an indicated pointer 3 (not shown), as is customary in electrical meters, the axially directed portion of such pointer being afforded egress from the assembly proper through one or the other of the arcuate slots 16a and 17a, in the end plates 16 and 17, respectively.

Should use of a taut-band coil suspension be desired, as opposed to the pivot type, my movement assembly is well adapted to that end. Indeed, in a movement asernbly according to my invention, the whole axial region is unobstructed, thus affording ample room for any desired type of coil suspension arrangement.

It will be understood that any suitable arrangements may be made for connecting the terminals of coil 22 to an external circuit. In pivot-type instruments, this is often done by utilizing hair springs as current conductors, while in taut-band instruments the suspensory filaments themselves are usually employed for that purpose. No specific disclosure of such external connection means is made in this specification, since they are conventional.

In the course of being assembled, the various stationary parts of my novel meter movement are of course rigidly secured together, by soldering, cementing, or other suitable means. On completion, the whole assembly is not only physically compact but remarkably rugged. Moreover, because the entire air gap is enclosed within the magneticcircuit components of the structure, my movement exhibits especially good self-shielding properties.

The flux paths in the magnetic circuit of my meter movement are graphically represented in FIG. 3. As therein indicated, like poles of the magnets 11 and 12 are disposed in facing relationship, thus affording one polarityof magnetic charge to the face plates 14 and 15 and the surface ring 13, these last-mentioned elements being those which define the outer boundary of the air gap within which the coil 22 moves. The inner boundary of that air gap, which is defined by core ring 21, is charged magnetically in the opposite polarity by virtue of the magnetic path afforded by the top plate 16, the bottom plate 17, and the core ring supports 18 and 19. In consequence of this, an intense static magnetic field exists throughout the air gap which envelops coil 22 on three of its four sides.

In the practical design of instruments embodying my invention, the dimensions of the magnetically permeable components will of course be selected to avoid magnetic saturation.

While I have in this specification described in considerable detail a typical embodiment of my invention, it should be understood that the description is intended to be merely illustrative. The scope of my invention is to be determined primarily by reference to the appended claims. Also, with respect to the appended claims, it will be understood that such terms as cylindrical, ringshaped, and the like embrace and include conformations of the indicated character which have relieved zones or sectors appropriate to facilitate assembly of the instrument and completion of magnetic circuits therein, as illustrated generally in the drawings that form a part of this specification,

I claim:

1. In a wide angle DArsonval type meter movement comprising a pair of annular permanent magnets located in axially spaced apart relationship, said magnets being axially magnetized, with like polarity pole faces thereof facing one another, an annular core ring interposed between said permanent magnets and axially aligned therewith, the opposite surfaces of said core ring being spaced from the adjacent surfaces of said permanent magnets, and a coil fitted around said core ring, said coil having freedom of movement relative to said core ring and relative to said permanent magnets, the improvement comprising mounting means for said core ring and said permanent magnets, said mounting means including a core ring support piece defining lateral recesses, said core ring having a relatively narrow separation in its wall, said separation being dimensioned whereby opposed ends of 4 the ring defining the separation are snugly received within said lateral recesses, said core ring support piece also including end portions on opposite sides of said lateral recesses, said permanent magnets each including openings adapted to receive said end portions, a cylindrical element co-axially disposed between said magnets with the opposite edges of the cylindrical element supporting the respective magnets and holding the magnets in spaced apart relationship, said cylindrical element surrounding said core ring with an annular space being defined between said core ring and said cylindrical element, said core ring support piece being magnetically permeable with the outer ends of the support piece magnetically interconnecting the the outer pole surfaces of said magnets, and said cylindrical element being magnetically permeable for magnetically interconneting the inner pole surfaces of said magnets.

2. A meter movement in accordance with claim 1 including magnetically permeable annular face plates magnectically attached to the inner and outer pole faces of each of said permanent magnets, said face plates being axially aligned with said magnets and said rings with the outer face plates being connected to said core ring support piece and with the inner face plate being connected to said cylindrical element.

3. A meter movement in accordance with claim 2 wherein the exposed outer surface of the combination comprising said face plates, said permanent magnets and said cylindrical elements defines a cylinder.

References Cited UNITED STATES PATENTS 591,241 10/1897 Shallenberger 324- 2,752,556 10/1951 Zar 324150 X 3,047,805 7/1962 Gersch 324150 RUDOLPH V. ROLINEC, Primary Examiner.

G. R. STRECKER, Assistant Examiner. 

